1. Field of the Invention
The present invention relates to a small-size image-formation optical system for use with image information processing apparatus, and more particularly to a small-size image-formation optical system utilizing Porro prism lenses for use with image information processing apparatus.
2. Description of the Prior Art
Conventionally, a small-size image formation optical system is disclosed in Japanese Patent Publication No. Sho 49-008,893, in which a strip lens array is employed. This strip lens array comprises a plurality of small-size lenses in the form of long, narrow plates arranged in an array, and the optical axes of the individual lenses are arranged in concurrence, with fixed spacing in a three-layer configuration. However, in this layered lens array construction, since an inverted image is formed in the intermediate lens array and is then converted to an erect image through a relay lens, the image performance is limited as to the degree of resolution and brightness. In addition, a shield plate is required to prevent flare between adjacent lenses, as is a diaphragm plate to compensate for irregularities in the quantity of light. Furthermore, even though a diaphragm plate is used, it is not possible to compensate for the irregularities in the quanitity of light in the direction of the array. Therefore, the use of the diaphragm plate for line-scanning in the direction of the array is not appropriate. In addition, because a suitable distance is usually necessary between the first and third lenses in a layered lens array, the distance between the object and the image becomes elongated, and the amount of possible miniaturization is limited.